Phew. This took me AGES, and is definitely the best windows song I ever made and the final I'm probably ever going to make. It combines 4 different versions on Windows:

1.) Windows 2000 - The ding effect here sounds awesome, and I made some good melodies with it. This part was the hardest to make, since I only had 4 sound effects of Windows 2000. One of them (the Chimes) had a seperate channel but it was reversed, which produced the sound you hear at the beginnin. In short, the sound at the beginning was a low, slowed down reverse version of the chimes.
2.) Windows XP - Heh, I'm used to making music with this ^^. This was the easiest for me, since I'm so used to making music with its sounds. I overused the Critical stop over here, though :\.
3.) Windows Vista (Beta) - The Battery Low sound is my favourite over here. Together with the System Hand and the Battery Critical, making a bassline with the Windows Vista Beta is child's play. The melodies over here were a little awkward to make since the instruments were difficult to work with, but I think I didn't do such a bad job on it.
4.) Windows Vista - This was quite hard to work with, since apart from the Default and Critical Stop, most of the other sound were pretty hard to make melodies out of. Still, I enjoyed using the Critical Stop over here, it's one of my favourite Windows sound effects :D (second to XP's unbeatable Critical Stop). There's a glitchy sound in this song which I made by reversing the Chimes of Windows Vista, as well.

As for the instruments and effects I used, I was spoilt for choice. In all, this uses 44 different sound effects, a reverse cymbal, as usual, and 14 different drum samples. I worked quite hard on the transitions in this song, so you'll hear a lot of reverse cymbals, drum rolls, high-to-low tomtom drums, etc. This also has the best drums I ever made in a song, and the most varied too, since it doesn't have a fixed drum beat.
At the end, after Windows 2000, XP, Vista (Beta) and Vista play all their melodies, my intention was to make them all play together, but unfortunately each batch of sound effects is in a different key, and don't have anything to do with each other, so that wasn't an option. Instead I made a melody play with one sound effect from one version, then being answered by another melody by another version, then being answered by another, etc. I messed up the ending a little over here, but apart from that, I think this is the best song I ever made, and the hardest I ever worked on, so please, just for once, 0-bomb some of my other windows songs, just not this one >_>.

Anyway, now that that's said, I'd like to thank Project8024, ImdoG and DaveGuy for giving me some nice ideas and being so supportive throughout my windows songs. By the way, if anyone thinks that the drums get annoying throughout the song, I can submit another version without drums. So, thanks for listening, and reading these crazily long Author's Comments. Enjoy the song, and votes and comments are greatly appreciated; I respond to all comments, and if the review is helpful, I usually review back.